temporal variation in precipitation." Ecology 94, no. (2013) "Sensitivity of grassland plant community composition to spatial vs. Species turnover is typically measured by partitioning diversity components into alpha and pairwise beta diversity. Replicate.var: A column that has same name and type as the replicate.var column, if replication is specified.Ĭleland, Elsa E., Scott L. Time.var: A column containing the second time point the name and type of this column is the same as the time.var column in the input dataframe. The name of this column is the same as the specified metric (default is "total"). Presence/absence of species was calculated over a global grid map, using the Mollweide projection, with 3,291 equal area cells of 220 × 220 km, which is an appropriate scale for global studies (Hurlbert & Jetz, 2007). Turnover: A numeric column with the turnover values. Species distributions for 1,473 living species of Muroidea were taken from the IUCN database (IUCN, 2008). The turnover function returns a data frame with the following attributes: A raw data table indicating how the m observed entities of interest have been classified into species according to the -classification (columns) and into sampling units (SU) according to the -classification (rows). Each replicate should reflect a single experimental unit - there must be a single abundance value per species within each time point and replicate. If multiple replicates are included in the data frame, that column should be specified with replicate.var. The input data frame needs to contain columns for time, species and abundance time.var, species.var and abundance.var are used to indicate which columns contain those variables. For example, if we are monitoring the effect that. Alpha diversity refers to the diversity within a particular area or ecosystem, and is usually expressed by the number of species (i.e., species richness) in that ecosystem. Total: The default metric, calculates summed appearances and disappearances relative to total species richness across both time periods.Īppearance: Calculates the number of species that appeared in the second time period relative to total species richness across both time periods.ĭisappearance: Calculates the number of species that disappeared in the second time period relative to total species richness across both time periods. Whittaker (1972) described three terms for measuring biodiversity over spatial scales: alpha, beta, and gamma diversity. The name of the optional replicate column Includes an option to compute turnover as just the proportion of species gained (i.e., "appearances") or lost (i.e., "disappearances").Ī data frame containing time, species and abundance columns and an optional column of replicates Computes species turnover between time periods as the proportion of species either gained or lost relative to the total number of species observed across both time periods.
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